ExternalIP is a String property used to specify the IP address used when the client sends the FTP PORT or EPRT commands behind a NAT-based firewall. 

ExternalIP must contain a non-empty string value when using a NAT-based firewall with the SSL transport. Set the value in ExternalIP to the IP address exposed to the outside world, or the NAT IP address on the Internet. 

Use DataPort, DataPortMin, and DataPortMax to indicate the port or port range to be forwarded to the NAT-based firewall.

DataPort 

DataPortMin 

DataPortMax 

Passive